macOS has the command `mkfile` to achieve the same:

    mkfile -n 10g temp_10GB_file

Syntax:

    mkfile [ -nv ] size[b|k|m|g] filename ...

And here&#39;s the related [manual page](https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man8/mkfile.8.html) for `mkfile`

*Cross Platform Alternative (Unix including macOS)*:

As an alternative you could also you the Unix util `dd`:

    dd if=/dev/zero of=temp_10GB_file bs=1 count=0 seek=10G

Note that on macOS you need to use a lowercase for the unit as follow:

    dd if=/dev/zero of=temp_10GB_file bs=1 count=0 seek=10g

And here&#39;s the related [manual page](https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man1/dd.1.html) for `dd`

I have a data frame that looks like this:
   
    #df
    ID  DRUG FED  AUC0t  Tmax   Cmax
    1    1     0   100     5      20
    2    1     1   200     6      25
    3    0     1   NA      2      30 
    4    0     0   150     6      65
Ans so on. I want to summarize some statistics on AUC, Tmax and Cmax by drug `DRUG` and FED STATUS `FED`. I use dplyr. For example: for the AUC:
 
    CI90lo &lt;- function(x) quantile(x, probs=0.05, na.rm=TRUE)
    CI90hi &lt;- function(x) quantile(x, probs=0.95, na.rm=TRUE)  
    
    summary &lt;- df %&gt;%
	             group_by(DRUG,FED) %&gt;%
                 summarize(mean=mean(AUC0t, na.rm=TRUE), 
                                     low = CI90lo(AUC0t), 
                                     high= CI90hi(AUC0t),
                                     min=min(AUC0t, na.rm=TRUE),
                                     max=max(AUC0t,na.rm=TRUE), 
                                     sd= sd(AUC0t, na.rm=TRUE))


However, the output is not grouped by DRUG and FED. It gives only one line containing the statistics of all by not faceted on DRUG and FED.

Any idea why? and how can I make it do the right thing?


Why are my dplyr group_by &amp; summarize not working properly? (name-collision with plyr)

I have a method that takes a list and returns an object:

    # input a list, returns an object
    def map_to_obj(lst):
        a_list = f(lst)
        return a_list[0] if a_list else None


I want to get a list that contains all the mapped elements that aren&#39;t `None`.

Like this:

    v_list = [v1, v2, v3, v4]

    [map_to_obj(v) for v in v_list if map_to_obj(v)]

But it doesn&#39;t seem good to call the `map_to_obj` method twice in the list comprehension. 

Is there a way to have local variables in list comprehensions so that it can have better performance? 

Or does the compiler optimize it automatically?

Here is what I want:

    (sml like)
    [let mapped = map_to_obj(v) in for v in v_list if mapped end] 


How to set local variable in list comprehension?

In order to create a 10 GB temp file...

In Linux you can do this:

    fallocate -l 10G temp_10GB_file

In Windows you can do this:

    fsutil file createnew temp_10GB_file 10000000000

...but what about if you&#39;re in OS X?

Quickly create a large file on a Mac OS X system?

In order to create a 10 GB temp file...
In Linux you can do this:
<pre><code class="hljs">fallocate -l 10G temp_10GB_file
</code></pre>
In Windows you can do this:
<pre><code class="hljs">fsutil file createnew temp_10GB_file 10000000000
</code></pre>
...but what about if you're in OS X?

**Problem:** NSAttributedString takes an NSRange while I&#39;m using a Swift String that uses Range&lt;String.Index&gt;
   
    let text = &quot;Long paragraph saying something goes here!&quot;
    let textRange = text.startIndex..&lt;text.endIndex
    let attributedString = NSMutableAttributedString(string: text)
    
    text.enumerateSubstringsInRange(textRange, options: NSStringEnumerationOptions.ByWords, { (substring, substringRange, enclosingRange, stop) -&gt; () in
        
        if (substring == &quot;saying&quot;) {
            attributedString.addAttribute(NSForegroundColorAttributeName, value: NSColor.redColor(), range: substringRange)
        }
    })

**Produces the following error:**

&gt; error: &#39;Range&lt;String.Index&gt;&#39; is not convertible to &#39;NSRange&#39;
&gt;         attributedString.addAttribute(NSForegroundColorAttributeName, value: NSColor.redColor(), range: substringRange)


NSRange from Swift Range?

I have a new mac pro (OS X 10.9.5) that I get to set up from scratch. I want to install RVM and the first thing it says to do is: 

&gt; Install mpapis public key (might need `gpg2` and or `sudo`)
&gt;
&gt;     gpg --keyserver hkp://keys.gnupg.net --recv-keys D39DC0E3

When I tried I got:

    gpg --keyserver hkp://keys.gnupg.net --recv-keys D39DC0E3
    zsh: command not found: gpg

I&#39;ve tried to find a good guide on how to overcome this that also looks trustworthy but I&#39;ve had no luck.

Can someone explain what `gpg` is, why I dont already have it, and how do I get it the right way.

How to resolve &quot;gpg: command not found&quot; error during RVM installation?

Does anyone know of a way to get a users time zone in Swift? 

I&#39;m getting a specific time something is on t.v. out of a database and then need to subtract/add from where they are located to show them the correct time it&#39;s on.


How to get a user&#39;s time zone?

I have a very simple question. I am brand new to Mac and I am trying to get my Java project moved over to my new Mac. The project has a Gradlew file that I thought I could run from the command line to build and run on any machine. When I do gradlew from the command line (in the location of the gradlew file) it says gradlew not found. Am I missing something on how to run a command from a bash shell?

How to run Gradle from the command line on Mac bash

I am trying to get the difference between the current date as `NSDate()` and a date from a PHP `time();` call for example: `NSDate(timeIntervalSinceReferenceDate: 1417147270)`. How do I go about getting the difference in time between the two dates. I&#39;d like to have a function that compares the two dates and `if(seconds &gt; 60)` then it returns minutes, `if(minutes &gt; 60)` return hours and `if(hours &gt; 24)` return days and so on. 

How should I go about this?

EDIT: The current accepted answer has done exactly what I&#39;ve wanted to do. I recommend it for easy usage for getting the time between two dates in the form that that PHP `time()` function uses. If you aren&#39;t particularly familiar with PHP, that&#39;s the time in seconds from January 1st, 1970. This is beneficial for a backend in PHP. If perhaps you&#39;re using a backend like NodeJS you might want to consider some of the other options you&#39;ll find below.

Content Type	Original Author	Original Content on Stackoverflow
Question	fredrik	View Question on Stackoverflow
Solution 1 - Macos	reto	View Answer on Stackoverflow

Quickly create a large file on a Mac OS X system?

Macos Problem Overview

Macos Solutions

Solution 1 - Macos

How to set local variable in list comprehension?

Why are my dplyr group_by & summarize not working properly? (name-collision with plyr)

Attributions